FIG. 1 shows an overview of an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) 100 in accordance with the prior art. As shown in FIG. 1, the E-UTRAN 100 includes three Evolved Node-Bs (eNBs) 102. However, any number of eNBs 102 may be included in the E-UTRAN 100. The eNBs 102 are interconnected by an X2 interface 108. The eNBs 102 are also connected by an S1 interface 106 to an Evolved Packet Core (EPC) 104. The EPC 104 includes a Mobility Management Entity (MME) 112 and a Serving Gateway (S-GW) 110.
FIG. 2 is a flow diagram of an Evolved Packet System (EPS) Mobility Management (EMM) Service Request (ESR) procedure 200 in accordance with the prior art. At step 202, a wireless transmit receive unit (WTRU) transmits an ESR message to an eNB. At step 204, the WTRU starts a timer, such as timer T3417ext, for example. At step 206, the WTRU enters an EMM-SERVICE-REQUEST-INITIATED state. At step 208, the WTRU determines that a user plane radio bearer is set up and therefore the ESR procedure 200 is successful. At step 210, the WTRU stops the timer and enters an EMM-REGISTERED state.
FIG. 3 is a signal diagram of an ESR procedure 300 in accordance with the prior art. An eNB 302 transmits a circuit switched (CS) call request 304 to a WTRU 306. The eNB 302 also transmits a CS service notification 308 to the WTRU 306. The WTRU 306 responds to the eNB 302 with an ESR message 310. The WTRU 306 then starts a timer 312. If the Non-Access Stratum (NAS) security mode control procedure is completed 314, or if NAS radio bearers are established 316 or a service reject message 318 is received by the WTRU 306, the timer is stopped 320.
If the WTRU 306 is in an EMM-CONNECTED mode when the ESR 310 is transmitted to the network, NAS security 314 may already be established. Furthermore, if the WTRU 306 receives a change cell message or a handover command, no bearers are setup. Consequently, other than receiving a service reject message, which indicates a failure of the ESR procedure 300, the WTRU 306 will not stop the timer even though the ESR procedure 300 was successful.
In addition, if the WTRU 306 is in EMM-IDLE mode and transmits the ESR message 310 to the eNB 302 for a CS fallback request, the network may not initiate the security mode procedure. The security mode procedure is a network operator option and may not be implemented by all operators. In this instance, the WTRU 306 may not use the completion of the security mode procedure as an indication to stop the timer, and the timer may continue to run.
The foregoing discussion with respect to LTE is provided as an example and may have applicability to other wireless technologies and standards. Furthermore, while the foregoing discussion is with respect to a timer, one skilled in the art may recognize that any time keeping or control device, such as a counter, may be used in place of the timer.